1. Field of the Invention
The present invention relates to a vehicle headlamp. More particularly, the present invention relates to a vehicle headlamp characterized in that: the efficiency of utilizing light emitted by a light source is high; the size of the vehicle headlamp is small; and the headlamp is capable of emitting a large quantity of light.
2. Related Art
Disclosed in JP-A-05-159603 a projector type lighting device unit that projects light to a front side of a vehicle.
The projector type lighting device unit irradiates the front side of the lighting device unit with light as follows. Light emitted by a light source, which is arranged in a vicinity on an optical axis extending in the longitudinal direction of a vehicle, is condensed and reflected by a reflector to the front side being concentrated upon the optical axis. The reflected light is irradiated to the front side of the lighting device unit via a projection lens provided in a front portion of the reflector. In the case where a light distribution pattern having a cutoff line in an upper end portion is formed by the lighting device unit, a shade is arranged in a vicinity of a rear side focus of the projection lens. A portion of the reflected light sent from the reflector is shaded by the shade so that the cutoff line is formed.
However, in the vehicle headlamp of JP-A-05-159603, the light emitted by the light source is once reflected by the reflector before the light is incident upon the projection lens, and the reflected light is condensed and incident upon the projection lens. Therefore, when the light is reflected on the reflector, a luminous intensity of the light is attenuated and a quantity of light is reduced. In addition, in the vehicle headlamp of JP-A-05-159603, the light, which is emergent from the light source and reflected on a lower half portion of the reflector, is shaded by the shade for forming the cutoff line. Therefore, only a substantial half of the quantity of the light incident upon the reflector is projected by the projection lens at the most. Accordingly, the efficiency of utilizing light emitted by the light source is low in the vehicle headlamp. It can be said that the light emitted by the light source is not effectively utilized.